The present technology relates to a flexible fuel cell, that is, a fuel cell which is flexible. More particularly, the present technology relates to a biofuel cell in which an enzyme is used as a reaction catalyst.
Biofuel cells in which an oxidoreductase is used as a reaction catalyst are advantageous in that electrons can be efficiently taken out from a fuel which cannot be utilized with ordinary industrial catalysts, such as glucose and ethanol. In view of this, the biofuel cells are expected as next-generation fuel cells high in capacity and safety. FIG. 7 shows a reaction scheme of a biofuel cell in which an enzyme is used. For example, in the case of a biofuel cell using glucose as a fuel, as shown in FIG. 7, an oxidation reaction of glucose proceeds and electrons are taken out at a negative electrode (anode), whereas a reduction reaction of oxygen (O2) in the atmospheric air proceeds at a positive electrode (cathode).
On the other hand, casings of ordinary cells are formed from a material poor in flexibility, such as metal. This is for preventing fuel crossover which might arise from damage to an electrolyte membrane or structural strain under an external stress, or for preventing flow-out of, for example, a solution from inside the cell due to breakage of the cell. Further, in the cells according to related art, an electrolyte or a catalyst layer inside the cell may also be formed by use of a hard material which lacks flexibility.
Similarly, in biofuel cells, casings made of a plastic or metal have been used. For instance, Japanese Patent Laid-open No. 2008-282586 proposes a button cell or tubular cell in which a metallic casing is used. Besides, Japanese Patent Laid-open No. 2009-048848 proposes a cubic cell in which a plastic-made casing is used.